Extinction of plasma arcs

ABSTRACT

A circuit configuration reduces electrical energy stored in a lead inductance formed by a plurality of leads that connect a power supply unit with a load. The circuit configuration includes a switching device in operative connection with at least one of the leads for enabling or interrupting power to the load. The circuit configuration also includes a first electrical nonlinear device arranged in parallel with the switching device; an energy storing device arranged in parallel with the switching device and in series with the first electrical nonlinear device; and a pre-charging circuit in operative connection with the energy storing device for charging the energy storing device to a pre-determined voltage level while power to the load is enabled.

CROSS REFERENCE TO RELATED APPL1CATION

This application claims priority under 35 U.S.C. § 119(a) to European Application No. 07 009 567.4, filed on May 12, 2007, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present description relates to a circuit for reducing electrical energy stored in a lead inductance of leads that connect a power supply unit with a load, for example, a plasma application.

BACKGROUND

Strong electrical current flowing from a power supply to a load, such as a plasma device or a plasma chamber used in plasma applications, for example, surface treatments or the like, through leads or cables of significant length is can cause a significant amount of electrical energy, which is stored in the lead inductance. In the present context, a lead is any electrical connection, such as a wire or the like, that can be associated with a non-negligible inductance value. When using a power supply apparatus for supplying power to a plasma process, plasma arc discharges or plasma arcs can occur inside the plasma chamber and can cause unwanted results.

SUMMARY

Typically, upon detection of an arc discharge in a plasma, power to the plasma application is interrupted. However, not only should the power supply be decoupled from the plasma as soon as possible, but also the amount of energy that is subsequently delivered from the lead inductance to the arc discharge should be decreased. One way to ensure this is by using relatively short leads or cables of low inductance, since the inductance value of a lead is generally proportional to the lead length. Thus, a circuit configuration, a power supply apparatus, and methods of the above-defined types, are described that ensure significant reduction of lead inductance energy delivered to a load without placing constraints on the relative locations of a power supply unit and the load, to which power is to be supplied.

According to a first general aspect a circuit configuration includes a first electrical nonlinear device arranged in parallel with a switching device; and an energy storing device arranged in parallel with the switching device and in series with the first electrical nonlinear device.

The nonlinear device is a device in which the current is not proportional to the voltage. A typical nonlinear device is an electrical valve device such as a diode. An electrical switch such as a transistor, a thyristor, or a triac, as well as a varistor or an electromechanical or magnetic device with nonlinear behavior can also be considered as an electrical valve device and therefore as a nonlinear device.

The energy storing device can be any device that is able to store energy. Typical energy storing devices are capacitances, inductances, or arrangements containing both, at least one capacitance and at least one inductance.

According to some aspects, a power supply apparatus can be designed with this circuit configuration.

In other general aspects, a method of reducing electrical energy stored in a lead inductance includes the steps of: prior to interrupting the power supply, pre-charging the energy storing device arranged in parallel with the switching device to a pre-determined energy level; interrupting the power supply; and discharging electrical energy stored in the energy storing device prior to re-enabling the power supply.

In other general aspects, a method for arc extinction in plasma applications includes performing the method described above in connection with interrupting power supply to the plasma application.

In some aspects, a circuit configuration reduces electrical energy stored in a lead inductance that is formed by a plurality of leads for connecting a power supply unit with a load. The circuit configuration includes a switching device in operative connection with at least one of the leads and configured to enable power to be supplied to the load, a first electrical nonlinear device in parallel with the switching device, an energy storing device in parallel with the switching device and in series with the first electrical nonlinear device, and a pre-charging circuit in operative connection with the energy storing device and being configured to store energy in the energy storing device to a pre-determined energy level while power supply to the load is enabled by the switching device.

Implementations can include one or more of the following features. For example, the first electrical nonlinear device can include a valve device. The valve device can be a diode.

The energy storing device can be a capacitive device.

The first electrical nonlinear device can be configured to block a pre-charging current from the pre-charging circuit for storing energy in the energy storing device.

The pre-charging circuit can be a voltage-controlled externally powered unit. The pre-charging circuit can include a second electrical nonlinear device connected between one of the leads and a node located between the energy storing device and the first electrical nonlinear device.

One or more of the first electrical nonlinear device and the second electrical nonlinear device can be a diode or a controlled MOSFET. The first and second electrical nonlinear devices can be arranged with opposite blocking directions.

The circuit configuration can include a discharging circuit in operative connection with the energy storing device to discharge electrical energy stored within the energy storing device. The discharging circuit can be integrated with the pre-charging circuit. The discharging circuit can include a resistive element connected in parallel with the second electrical nonlinear device, and a discharge switching device connected to the energy storing device for discharging the energy storing device through the resistive element.

The plurality of leads can connect the power supply unit with a plasma application.

The circuit configuration can include a power supply unit that supplies power to the load.

In other general aspects, a power supply apparatus for plasma applications includes a power supply unit; and outputs for supplying power from the power supply unit to a plasma application through a plurality of leads. The power supply apparatus includes a first circuit configuration for reducing electrical energy stored in a lead inductance that is formed by the plurality of leads. The circuit configuration includes a switching device in operative connection with at least one of the leads and configured to enabling power to be supplied to the load; a first electrical nonlinear device in parallel with the switching device; an energy storing device in parallel with the switching device and in series with the first electrical nonlinear device; and a pre-charging circuit in operative connection with the energy storing device and configured to store energy in the energy storing device to a pre-determined energy level while power supply to the load is enabled by the switching device.

Implementations can include one or more of the following features. For example, the power supply apparatus can include a control unit that monitors an operational state of the plasma application, and controls at least the switching device in response to a result of the monitoring. The power supply unit can be a direct current power supply unit.

The power supply unit can be an alternating current power supply unit.

In other general aspect, a method can be performed to reduce electrical energy stored in a lead inductance formed by a plurality of leads that connect a power supply unit with a load. The method includes interrupting power to the load with a switching device that is in operative connection with at least one of the leads; prior to interrupting the power, pre-charging an energy storing device arranged in parallel with the switching device to a pre-determined energy level while the switching device is closed; opening the switching device; and discharging electrical energy stored in the energy storing device prior to closing the switching device.

In another general aspect, a method can be performed for arc extinction in plasma applications supplied by a direct-current power supply unit. The method includes monitoring an operational state of the plasma application with respect to an occurrence of plasma arcs; interrupting power supply to the plasma application in response to a result of the monitoring by interrupting power to the plasma application by opening a switching device that, when closed, connects the direct-current power supply unit with the plasma application; pre-charging an energy storing device arranged in parallel with the switching device to a pre-determined energy level while the switching device is closed; and discharging electrical energy stored in the energy storing device prior to closing the switching device after power to the load has been interrupted by opening the switching device.

Implementations can include one or more of the following features. For example, the method can include applying an adjustable blocking time after interrupting power to the plasma application, during which a further interruption of power supply to the plasma application is inhibited.

In some general aspects, a method is performed for reducing electrical energy stored in a lead inductance formed by a plurality of leads that connect a power supply unit with a plasma application. The method includes pre-charging an energy storing device arranged in parallel with a switching device that is connected to at least one of the leads to a pre-determined energy level while the switching device is closed; interrupting power to the load by opening the switching device; and discharging electrical energy stored in the energy storing device prior to closing the switching device after power to the load has been interrupted by opening the switching device.

The circuit configuration, power supply apparatus, and methods described in this description ensure a significant reduction of the energy transferred from the lead inductance to the arc discharge without relying on any shortening of leads or cables. In this way, improved arc extinction and plasma application is enabled without placing constraints on the relative location of power supply unit and the load.

A switching device is located between the power supply unit and the load, for example, a plasma application. The switching device is closed during normal operating conditions, and an energy storing device connected in parallel with the switching device is pre-charged to a required energy (voltage) level by means of a pre-charging circuit. The latter can be devised as a voltage-controlled externally powered unit. When an arc is detected in the plasma, that is, when a load condition requires interruption of power supply together with a reduction of residual energy from the leads being delivered to the load, the switching device is opened so that an output current from the lead inductances flows along a bypass path. The bypass path includes the energy storing device connected in series with an electrical nonlinear device, for example, a diode. This particular arrangement enables transferring a large amount of the residual energy stored in the lead inductance into the energy storing device instead of delivering it to the load, for example, to an arc discharge.

Excessive energy stored in the energy storing device can be eliminated by means of a discharging circuit prior to re-enabling power supply to the load.

The circuit configuration can be arranged so that the switching device is either arranged on a positive side of the power supply unit or on a negative side of the power supply unit.

The pre-charging circuit and the discharging circuit can be integrated in a common circuit entity. Alternatively, the pre-charging circuit and the discharging circuit can be separate circuits. In particular, the discharging circuit can include an electrical nonlinear device (for example, a diode) and a resistive element (for example, a discharge resistor) connected in parallel.

Since both the switching device and the discharge resistor can heat up considerably during operation, any one of the elements can be equipped with a heat sink structure in order to efficiently dissipate excess heat.

The diodes that are used in the circuit configuration can alternatively be devised as controlled metal oxide semiconductor field effect transistors (MOSFETs).

In particular, when using the circuit configuration in connection with arc extinction for plasma applications, detecting (and extinguishing) an excessive number of plasma arcs can cause the discharge resistor to heat. In this context, an adjustable blocking time can be applied after interrupting power supply to the plasma application. During the blocking time, any further interruption of power supply to the plasma application is inhibited. In other words, a subsequent plasma arc extinction is only enabled after the blocking time has ended. Additionally, this feature also enables “swapping” of charges in the pre-charging/discharging circuits.

The power supply apparatus can also include a second circuit configuration of the type described above and being connected antiparallel with the circuit configuration. The power supply unit can either be a direct current power supply or an alternating current power supply.

Further advantages and characteristics of the present invention can be gathered from the following description given by way of example only with reference to the enclosed drawings. Features mentioned above as well as below can be used either individually or in conjunction. The following description is not to be regarded as an exhaustive enumeration but rather as examples with respect to a general concept underlying the present invention.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of a first implementation of a power supply apparatus including a first implementation of a circuit configuration;

FIG. 2 is a circuit diagram of a second implementation of a power supply apparatus including a second implementation of a circuit configuration;

FIG. 3 is a circuit diagram of a third implementation of a power supply apparatus including a third implementation of a circuit configuration;

FIG. 4 is a circuit diagram of a fourth implementation of a power supply apparatus including a forth implementation of a circuit configuration; and

FIG. 5 is a flow chart of a procedure for arc extinction in plasma applications a procedure for reducing electrical energy.

DETAILED DESCRIPTION

FIG. 1 shows a circuit diagram of a power supply apparatus 1 that is connected with a plasma application 2, for example, in the form of a plasma device or a plasma chamber, through leads 3.1, 3.2, which are connected to respective outputs 4.1, 4.2 of the power supply apparatus 1. The leads 3.1, 3.2 can be arranged in a common cable and present respective lead inductances L1, L2, thus forming a total lead inductance L=L1+L2. The leads 3.1, 3.2 can be, for example, two-conductor insulated coaxial cables, one or more twisted-pair cables, or networks of cables such as a simple conductor hookup or quadrupole connections. The total lead inductance L can store electrical energy during operation of the power supply apparatus 1, that is, during operation of plasma application 2.

The output 4.1 of the power supply apparatus 1 is connected with a positive pole (+) of a direct current (DC) power supply unit (or generator) 5 in the power supply apparatus 1. Likewise, the output 4.2 of the power supply apparatus 1 is connected with a negative pole (−) of the DC power supply unit 5. An electrical nonlinear device in form of a freewheeling diode D1 is coupled in reverse bias across the positive and negative poles of the power supply unit 5.

Between the negative pole (−) of the power supply unit 5 and the output 4.2 of the power supply apparatus 1 is a switching device SS in the form of a serial switch. For instance, the serial switch SS could be devised in the form of an insulated-gate bipolar transistor (IGBT) or a MOSFET. The serial switch SS is a switch that can be switched on and off at a given time. In parallel with the serial switch SS is another electrical nonlinear device in the form of a diode D2. The diode D2 is connected in series with a capacitor C, so that both the diode D2 and the capacitor C are arranged in parallel with the serial switch SS, where the cathode of the diode D2 faces the capacitor C. In this way, the diode D2 and the capacitor C effectively form a bypass for the serial switch SS. The anode-side connecting node 6 of the diode D1 is located between the bypass and the negative pole (−) of the power supply unit 5.

The power supply apparatus 1 also includes a pre-charging/discharging circuit 7 that is coupled across terminals of the capacitor C. The pre-charging/discharging circuit 7 can be made as a voltage-controlled, externally powered unit. The pre-charging/discharging circuit 7 includes a voltage source (not shown) for charging the capacitor C to a pre-determined and adjustable voltage level. To this end, the pre-charging/discharging circuit 7 presents positive and negative poles (+/−), where the positive pole (+) of pre-charging/discharging circuit 7 is connected between the capacitor C and the cathode of the diode D2, and the negative pole (−) of the pre-charging/discharging circuit 7 is connected between the capacitor C and the serial switch SS, that is, between the capacitor C and the anode-side connecting node 6 of the diode D1. In this way, the diode D2 is arranged in reverse bias with respect to the pre-charging potential of the pre-charging/discharging circuit 7 and is adapted to block a pre-charging current from the pre-charging circuit/discharging circuit 7 for the charging capacitor C.

The capacitor C could be replaced with any sort of energy storing device. For example, the capacitor C could be replaced with an inductor that acts as an energy storing device and the pre-charging/discharging circuit 7 is preferably devised as a current-controlled, externally powered unit. Such an energy storing device can be useful if energy stored in the load is in the form of a capacitance, for example, a capacitance of the plasma.

The power supply apparatus 1 further includes a control unit 8 that can perform one or more of control and monitoring functions, as explained in detail below. In other implementations, the control unit 8 could be external to the power supply apparatus 1. The Control unit 8 is operatively connected with the serial switch SS, the pre-charging/discharging circuit 7, the power supply unit 5, and the plasma application 2. In some implementations, the control unit 8 is a plasma arc detection/extinction unit, and is adapted for monitoring an operational state of the plasma application 2 for detecting occurrences of plasma arcs in order to control operation of the serial switch SS, the pre-charging/discharging circuit 7, or both in response to the monitoring of the plasma application 2. The control unit 8 can be adapted to detect plasma arcs directly by monitoring the plasma application 2, that is, from plasma parameters. Alternatively or additionally, the control unit 8 can be adapted to do so indirectly by monitoring operational parameters of the power supply unit 5, for example, the output voltage, the output current, or both of the power supply unit 5.

Extinction of detected plasma arcs is generally accomplished by interrupting power supplies to the plasma application 2 by opening the serial switch SS under control of the control unit 8. Further to this, the design of FIG. 1 ensures a reduction in lead inductance energy to enable faster arc extinction in plasma applications.

The operation of the power supply apparatus 1 will now be described in detail. Under normal operating conditions, that is, with no arcs detected in plasma application 2, the serial switch SS is closed, and the pre-charging/discharging circuit 7 pre-charges capacitor C to the pre-determined voltage level. When a plasma arc is detected by the control unit 8, the serial switch SS is opened under control of the control unit 8, thus forcing an output current in the lead inductances L1, L2, which will generally be increased due to the occurrence of a plasma arc, to flow through the diode D2 against the initial pre-charged voltage of the capacitor C and then further through the freewheeling diode D1 via the connecting node 6. In this way, the diode D2 effectively functions as a bypass diode for the opened serial switch SS. Owing to this particular arrangement, a considerable amount of residual electrical energy, which is mainly stored in the lead inductances L1, L2, is transferred into the capacitor C and stored therein instead of being delivered to the plasma arc or plasma arc discharge. This contributes to an accelerated extinction of plasma arcs. In other words, the total energy transferred to the arc discharge is significantly reduced.

Prior to re-closing the serial switch SS in order to re-establish power supplies to the plasma application 2, the excess electrical energy stored in the capacitor C is eliminated by means of the discharging function of the pre-charging/discharging circuit 7. Then, the serial switch SS can be safely closed under control of the control unit 8.

Optionally, the control unit 8 includes an additional function 8 a, which provides an adjustable blocking time, that is, a corresponding control signal (not shown) for controlling the serial switch SS, during which a further interruption of power supplied to the plasma application 2 is inhibited. In other words, when power supplied to the plasma application 2 is interrupted by opening the serial switch SS under control of the control unit 8, the blocking time function 8 a ensures that the serial switch SS cannot be opened again during the blocking time—if the serial switch SS has been closed in the meantime in order to re-establish power supplied to the plasma application 2. The adjustable blocking time enables an adjustable setting of a low arc detection rate, which can be important in order to allow the pre-charging/discharging circuit 7 to swap charges and to avoid excessive heating of the serial switch SS.

During the above-described operation of the power supply apparatus 1 considerable heat is dissipated at the serial switch SS; therefore, the serial switch SS can advantageously be equipped with a heat sink structure for dissipating excess heat, which is not shown in FIG. 1.

In this way, the serial switch SS, the bypass diode D2, the capacitor C, and the pre-charging/discharging circuit 7 together with the freewheeling diode D1 effectively constitute a circuit configuration 9 for reducing the electrical energy stored in the total lead inductance L formed by the leads L1, L2. The circuit configuration 9 has been highlighted with a dashed box in FIG. 1.

Both diodes D1 and D2 could be replaced by switches, which can be controlled by the control unit 8. With a plurality of the circuit configurations 9 that are connected antiparallel and with controllable switches instead of diodes D1, D2 the circuit arrangement consisting of at least two antiparallel circuit configurations 9 is also applicable to a system with a power supply unit 5 that feeds AC energy into the plasma application 2.

FIG. 2 shows a circuit diagram of another implementation of a power supply apparatus 1′ including another implementation of the circuit configuration. The power supply apparatus 1′ of FIG. 2 is generally similar to that of FIG. 1, which has been described in detail above, so that the following description focuses on differences between the designs of FIG. 1 and FIG. 2 only. It should also be noted that in FIG. 2 the control unit 8 has been omitted for mere reason of clarity, but the control unit 8 can connect to the switch SS, the power supply unit 5, the switch DS, and the plasma application 2.

Instead of the integrated pre-charging/discharging circuit 7 of FIG. 1, the power supply apparatus 1′ of FIG. 2 includes discrete pre-charging and discharging circuits 7.1, 7.2, respectively. The pre-charging circuit 7.1 is formed by an electrical nonlinear device in the form of a diode D3 connected between the positive pole (+) of the power supply unit 5 and a node 10, which is located between the capacitor C, the cathode of the diode D3, and the cathode of the bypass diode D2. The discharging circuit 7.2 is formed by a resistive element in the form of discharge resistor R connected between the output 4.1 of the power supply apparatus 1′ and a node 11, which is located between the node 10 and the cathode of the bypass diode D2. Furthermore, the discharging circuit 7.2 includes a discharge switching device DS coupled across the positive and negative poles (+/−) of the power supply unit 5 in parallel with the freewheeling diode D1. The diodes D2 and D3 are arranged with opposite blocking directions, that is, they are connected in a cathode-to-cathode type fashion.

Operation of power supply apparatus 1′ of FIG. 2 is as follows. Under normal operating conditions, the serial switch SS is closed. The capacitor C is charged through the diode D3 (charging diode) to an output voltage level of the power supply unit 5. Upon detection of an arc discharge in the plasma application 2, as previously described with reference to FIG. 1, the control unit 8 opens the serial switch SS, thus forcing an output current in the lead inductances L1, L2 to flow through the bypass diode D2 against the initial voltage of the capacitor C and then further through the freewheeling diode D1. Again, owing to this arrangement, a large amount of the residual energy stored in the total lead inductance L is transferred into the capacitor C instead of being delivered to the arc discharge. As a result of this, the total energy transferred to the arc discharge is significantly reduced, thus contributing to accelerated arc extinction. Excess energy stored in the capacitor C is eliminated or reduced by means of the discharging circuit 7.2 prior to subsequent switching-on of the serial switch SS. Operation of the discharge switching device DS in the discharging circuit 7.2, that is, closing the switching device DS in order to discharge the capacitor C through the discharge resistor R, could also be controlled by the control unit 8 (shown in FIG. 1).

Instead of using regular diodes, any one of electrical nonlinear devices D1-D3 could alternatively be a suitably controlled MOSFET, controlling of which could also be provided by the control unit 8 (shown in FIG. 1).

FIG. 3 shows a circuit diagram of another power supply apparatus 1″ that includes a third implementation of the circuit configuration. Again, the power supply apparatus 1″ of FIG. 3 generally corresponds to that of FIG. 1 so that only differences between these two is explained here in detail. As in FIG. 2, the control unit 8 has been omitted for reason of clarity only; the control unit 8 is connected to the switch SS, the plasma application 2, the circuit 7, and the power supply unit 5.

In contrast to the power supply apparatus 1 of FIG. 1, in the power supply apparatus 1″ of FIG. 3, the serial switch SS is arranged on the positive side of the power supply unit 5, that is, is directly connected with the positive pole (+) of the power supply unit 5. Consequently, the configuration of the bypass path including the bypass diode D2, the capacitor C, and the integrated pre-charging/discharging circuit 7 has been modified accordingly. It should be noted that the bypass diode D2 is in this apparatus 1″ connected with the capacitor 10 by means of its anode instead of being connected to the capacitor C via its cathode, as it is in FIG. 1.

Operation of the power supply apparatus 1″ of FIG. 3 is similar to that of the power supply apparatus 1 of FIG. 1 so that a detailed description of its operation can be omitted.

FIG. 4 shows a circuit diagram of a power supply apparatus 1′″ including a forth implementation of the circuit configuration. The power supply apparatus 1′″ of FIG. 4 is a variation of the power supply apparatus 1′ of FIG. 2. As in the power supply apparatus 1″ of FIG. 3, the serial switch SS is located on the positive side (+) of the power supply unit 5 in the power supply apparatus 1′″ of FIG. 4. Thus, the capacitor C and the bypass diode D2 are re-arranged in the power supply apparatus 1′″ relative to the embodiment of FIG. 2, as previously described with reference to FIG. 3. The charging diode D3 is connected between the negative pole (−) of the power supply unit 5 and the node 10′, which is located between the anode of the charging diode D3 and the capacitor C. The discharge resistor R is connected in parallel with the charging diode D3, so that one terminal of the discharge resistor R is connected with the negative pole (−) of the power supply unit 5 while the other terminal of the discharge resistor R is connected with the node 11′ located between the node 10′ and the anode of the bypass diode D2. The diodes D2, D3 are connected in anode-to-anode type fashion, that is, with opposite blocking directions. While the charging diode D3 of FIG. 4 effectively forms a pre-charging circuit 7.1′, the switching device DS and the resistor R effectively form a discharging circuit 7.2′.

Operation of the power supply apparatus 1′″ of FIG. 4 corresponds to the operation of the power supply apparatus 1′ previously described with reference to FIG. 2. Therefore, a detailed description thereof can be omitted.

As previously described in connection with the serial switch SS, the discharge resistors R of FIG. 2 and FIG. 4 can dissipate a considerable amount of heat during operation of the power supply apparatus 1′ or 1′″. Therefore, the discharge resistors R, too, can be equipped with heat sink structures (not shown) in order to efficiently dissipate excess heat.

FIG. 5 is a flow chart of a procedure for arc extinction in plasma applications that reduces electrical energy supplied to a load. The method starts with step S100 and can be performed, for example, at least in part by software within the control unit 8. Initially, assuming normal operation of the power supply apparatus 1, 1′, 1″, 1′″, that is, no arc discharges are detected in the plasma application 2, temporal blocking of power supply interruption is deactivated.

In step S102, the energy storing device (capacitor C) is (pre-)charged, as previously described. Then, in step S104, an operating state of the plasma application 2 is monitored, for example, by the control unit 8 (shown in FIG. 1), as previously described. Steps S102 and S104 can be performed simultaneously or nearly simultaneously.

Then, in step S106 it is decided whether an arc discharge has been detected. If the question in step S106 (“arc detected?”) is answered in the affirmative (y), in subsequent step S108, it is checked whether temporal blocking of power supply interruption has been deactivated. Assuming a deactivated state of temporal blocking, the question in step S108 (“temporal blocking of power supply interruption deactivated?”) is answered in the affirmative (y) so that in subsequent step S110 the serial switch SS is opened, thus interrupting the power supplied to the plasma application 2 for arc extinction. Furthermore, residual electrical energy stored in the lead inductances L1, L2 is transferred to the energy storing device (capacitor C), as previously described. After a pre-determined (adjustable) amount of time, the energy storing device C is discharged in step S112. Then, in step S114, temporal blocking of power supply interruption to plasma application 2 is activated. In subsequent step S116 the serial switch SS is closed, thus re-establishing power supplied to the plasma application 2. In some implementations, step S114 could alternatively be performed before step S112 or after step S116. If the question in step S106 (“arc detected?”) is answered in the negative (n), then the method returns to step S104, that is, an operational state of the plasma application 2 is repeatedly monitored, for example, by the control unit 8.

After step S116, the method terminates with step S118. In practice, however, the method returns to step S102. It may now be assumed that the question in step S108 (“temporal blocking of power supply interruption deactivated?”) is answered in the negative (n), owing to performing step S114. In this case, from step S108 the method returns to step S104.

Other implementations are within the scope of the following claims.

For example, in other alternative implementations, the power supply apparatus of FIGS. 1-4 includes an alternating current (AC) power supply unit. In this case, the power supply apparatus or the circuit configuration can be designed to account for the AC power signal and therefore it can include additional components such as an additional capacitor. 

1. A circuit configuration for reducing electrical energy stored in a lead inductance that is formed by a plurality of leads for connecting a power supply unit with a load, the circuit configuration comprising: a switching device in operative connection with at least one of the leads and configured to enable power to be supplied to the load; a first electrical nonlinear device in parallel with the switching device; an energy storing device in parallel with the switching device and in series with the first electrical nonlinear device; and a pre-charging circuit in operative connection with the energy storing device and being configured to store energy in the energy storing device to a pre-determined energy level while power supply to the load is enabled by the switching device.
 2. The circuit configuration of claim 1, wherein the first electrical nonlinear device includes a valve device.
 3. The circuit configuration of claim 2, wherein the valve device is a diode.
 4. The circuit configuration of claim 1, wherein the energy storing device is a capacitive device.
 5. The circuit configuration of claim 1, wherein the first electrical nonlinear device is configured to block a pre-charging current from the pre-charging circuit for storing energy in the energy storing device.
 6. The circuit configuration of claim 1, wherein the pre-charging circuit is a voltage-controlled externally powered unit.
 7. The circuit configuration of claim 1, wherein the pre-charging circuit comprises a second electrical nonlinear device connected between one of the leads and a node located between the energy storing device and the first electrical nonlinear device.
 8. The circuit configuration of claim 7, wherein one or more of the first electrical nonlinear device and the second electrical nonlinear device is a diode or a controlled MOSFET.
 9. The circuit configuration of claim 7, wherein the first and second electrical nonlinear devices are arranged with opposite blocking directions.
 10. The circuit configuration of claim 1, further comprising a discharging circuit in operative connection with the energy storing device to discharge electrical energy stored within the energy storing device.
 11. The circuit arrangement of claim 10, wherein the discharging circuit is integrated with the pre-charging circuit.
 12. The circuit arrangement of claim 10, wherein the discharging circuit comprises: a resistive element connected in parallel with the second electrical nonlinear device; and a discharge switching device connected to the energy storing device for discharging the energy storing device through the resistive element.
 13. The circuit configuration of claim 1, wherein the plurality of leads connects the power supply unit with a plasma application.
 14. The circuit configuration of claim 1, further comprising a power supply unit that supplies power to the load.
 15. A power supply apparatus for plasma applications, the power supply apparatus comprising: a power supply unit; and outputs for supplying power from the power supply unit to a plasma application through a plurality of leads; wherein the power supply apparatus comprises a first circuit configuration for reducing electrical energy stored in a lead inductance that is formed by the plurality of leads, the circuit configuration comprising: a switching device in operative connection with at least one of the leads and configured to enabling power to be supplied to the load; a first electrical nonlinear device in parallel with the switching device; an energy storing device in parallel with the switching device and in series with the first electrical nonlinear device; and a pre-charging circuit in operative connection with the energy storing device and being configured to store energy in the energy storing device to a pre-determined energy level while power supply to the load is enabled by the switching device.
 16. The power supply apparatus of claim 15, further comprising a control unit that monitors an operational state of the plasma application, and controls at least the switching device in response to a result of the monitoring.
 17. The power supply apparatus of claim 15, wherein the power supply unit is a direct current power supply unit.
 18. The power supply apparatus of claim 15, wherein the power supply unit is an alternating current power supply unit.
 19. A method of reducing electrical energy stored in a lead inductance formed by a plurality of leads that connect a power supply unit with a load, the method comprising: interrupting power to the load with a switching device that is in operative connection with at least one of the leads; prior to interrupting the power, pre-charging an energy storing device arranged in parallel with the switching device to a pre-determined energy level while the switching device is closed; opening the switching device; and discharging electrical energy stored in the energy storing device prior to closing the switching device.
 20. A method for arc extinction in plasma applications supplied by a direct-current power supply unit, the method comprising: monitoring an operational state of the plasma application with respect to an occurrence of plasma arcs; interrupting power supply to the plasma application in response to a result of the monitoring by interrupting power to the plasma application by opening a switching device that, when closed, connects the direct-current power supply unit with the plasma application; pre-charging an energy storing device arranged in parallel with the switching device to a pre-determined energy level while the switching device is closed; and discharging electrical energy stored in the energy storing device prior to closing the switching device after power to the load has been interrupted by opening the switching device.
 21. The method of claim 20, further comprising applying an adjustable blocking time after interrupting power to the plasma application, during which a further interruption of power supply to the plasma application is inhibited. 